Hydrogen-embrittlement-inhibition with 1-ethynylcyclohexanol-1



United States Patent 3,340,197 HYDROGEN-EMBRITTLEMENT-INHIBITION WITHl-ETHYNYLCYCLOHEXANOL-l George Davidowich, Bayonne, and Morton W. Leeds,

Murray Hill, N.J., assignors to Air Reduction Company, Incorporated, NewYork, N.Y., a corporation of New York No Drawing. Filed Apr. 15, 1964,Ser. No. 360,100 2 Claims. (Cl. 2S2146) This invention relates to theprevention of hydrogen embrittlement in the treatment of ferrous metalswith aqueous acidic solutions, and is more particularly concerned withthe provision of an acidic aqueous solution inhibited against hydrogenembrittlement by reason of the inclusion in the solution of a hydrogenembrittlement inhibitor.

In the treatment of ferrous metals, i.e. iron, steel and other ferrousalloys, such as in metal cleaning operations, or in pickling operations,to remove rust, grease, scale, or other undesired surface materials orcoatings from the metal, e.g. in aqueous sulfuric acid solutions, theproblem of hydrogen embrittlement is encountered. As stated by Dr. CarlA. Zapffe in an article entitled, The Behavior of Hydrogen in SteelDuring Pickling (Wire and Wire Products, February 1946, pages l49157),hydrogen embrittlement of steel is a problem of long standing in plantsusing either acid or cathodic pickling, and hydrogen embrittlement isdefined as the trapment under high pressure of hydrogen gas within themicroscopic voids that traverse the interior of each grain of the metal.These voids, once congested sufiiciently with the gas, place the grainunder three dimensional stress, which precludes slip and plasticmovement. The metal is then embrittled. As stated in the foregoingarticle, the tremendous quantity of hydrogen that steel may occludewithin its microscopic voids is demonstrated by the pickling of a steelwire in sulfuric acid, followed by careful rinsing and drying, andsubsequent immersion of the wire in deaerated hot water. The wire, uponimmersion, produced a violent evolution, with the bubbling continuingvisibly for minutes.

It is customary in pickling metal cleaning, and like operations toinclude in the aqueous sulfuric acid solution a corrosion inhibitor toprevent or retard attack by the acidic solution upon the metal beingtreated, and such corrosion inhibitors are commonly used in pickling andrelated metal treating operations. However, as discussed by Zapffe etal. in a series of three articles entitled Evaluation of PicklingInhibitors from the Standpoint of Hydrogen Embrittlement, which appearedat pages 933- 939; 1048-1053, 1080-4082; and 1126-1130, 1172-1175; ofWire and Wire Products, vol. 23 (1948), the great majority of compoundswhich act as corrosion inhibitors and are sold commercially for thispurpose do not prevent hydrogen embrittlement and, indeed, actuallypromote and increase hydrogen embrittlement. In other words, thehydrogen embrittlement observed when these corrosion inhibitors are usedis greater than that observed when the same metal is pickled underidentical conditions in the raw sulfuric acid solution.

There is, therefore, an important need for hydrogen embrittlementinhibitors because the usual corrosion inhibitors cannot be relied onfor this purpose.

It is, accordingly, an object of this invention to provide ahydrogen-embrittlement inhibitor which is effective in aqueous sulfuricacid solutions to prevent hydrogen embrittlement of ferrous metalsimmersed in it.

It is a further object of the invention to provide an inhibited aqueoussulfuric acid solution suitable for the treatment of ferrous metalswithout hydrogen embrittlement.

It is a still further object of the invention to provide a method ofpreventing hydrogen embrittlement in the treatment of ferrous metalswith aqueous sulfuric acid solutions.

These and other objects of the invention are achieved by theincorporation in an aqueous sulfuric acid solution of a small buteffective hydrogen-embrittlement-inhibiting amount ofl-ethynylcyclohexanol-l. This compound is readily prepared by theprocess described in Tedeschi et a1. U.S. Patent No. 3,082,260 of Mar.19, 1963.

The introduction of the l-ethynylcyclohexanol-l in aqueous sulfuric acidsolutions has been found to have the desirable result of inhibiting orsubstantially preventing hydrogen embrittlement of iron or ferrousmetals immersed in the solution.

The use of l-ethynylcyclohexanol-l as a hydrogenembrittlement inhibitorin aqueous sulfuric acid solutions is advantageous in that itsinhibiting action is effective over a wide and useful concentrationrange. This inhibitor has the further advantage that it is effectiveeven at very low concentrations in the acidic solutions. A furtheradvantage of this inhibitor is that it may be used at elevatedtemperatures to provide good hydrogen embrittlement and even under theseconditions they are effective in very low concentrations.

The most elfective amount of l-ethynylcyclohexanol-l to be used inaccordance with this invention can vary, depending upon local operatingconditions. Thus, the temperature and other characteristics of theaqueous acid system may also have a bearing upon the amount of inhibitorto be used.

In general, however, it has been found that a concenr tration ofl-ethynylcyclohexanol-l between 0.01% to 0.5% by weight of the aqueoussulfuric acid solution is an effective hydrogen-embrittlement-inhibitingconcentration, with a concentration between 0.05% to 0.1% beingparticularly advantageous even for aqueous sulfuric acid systems atelevated temperatures, e.g. in the neighborhood of C. The sulfuric acidsolution can be dilute or concentrated and can be of any of theconcentrations used in treating ferrous metals, eg 5 to 80%.

The following specific example is illustrative of the corrosioninhibiting properties of the l-ethynylcyclohexanol-l of the invention.In the example, the inhibitor concentration is expressed as a percent byweight of the aqueous acidic solution in which it is incorporated andthe acid concentration of the solution is expressed as percent by weightof the solution.

The method used to determine the hydrogen-embrittlement-inhibitingproperties of the inhibitor of the invention as set forth in thefollowing examples is that developed by Zaptfe (Transactions AmericanInstitute of Metallurgical Engineers, Iron and Steel Div., vol. 167, pp.281- 282; 1946) which depends upon the bending or breaking of a piece ofwire which is bent around a constant radius through 180 at a constantrate. The rate of bending is 4.5 per second, which is rapid enough toprevent significant recovery from escaping hydrogen during bending, butnot too rapid to allow reading of the breaking angle.

Wire specimens 4 in. long cut from Arcrod No. 1 stainless steel 430welding wire in. diameter) were used in the tests. The specimens werecleaned with 400 S emery cloth. The clean specimens in duplicate wereplaced in a jar which contained ml. of 4.8 N sulfuric acid, plus theinhibitor. The jars were placed in a constant temperature oven andheated for 15 min. at 80 C. The specimens were then removed, rinsed inwater, dried, and the angle of bend determined. The bend angle indicatedin the table below is an average of at least four specimens.

3 Example 1 The following test results illustrate thehydrogen-embrittlement-inhibiting properties ofl-ethynylcyclohexanol- 1. Using the procedures described above,stainless steel wire specimens were immersed in 4.8 N sulfuric acid at80 C. (176 F.) for 15 minutes with the inhibitor concentration being0.05% and 0.01% of the acidic solution.

Inhibitor concentration, percent: Bend angle 0.05 No breaking at maximumangle. 0.01 Do. None (control) Broke at 45.

A particularly advantageous characteristic of l-ethynylcyclohexanol-l isthat this specific acetylenic alcohol not only is an outstandinginhibitor of hydrogen-embrittlement in aqueous sulfuric acid solutionssuch as those used in pickling, but it also functions as a highlyeffective corrosion inhibitor in such solutions. In other words, thisspecific acetylenic alcohol has been found to be a highly effectivehydrogen-embrittlement-inhibitor which also functions simultaneously asa corrosion inhibitor and thus avoids the need for using both acorrosion inhibitor and a separate hydrogen-embrittlernent-inhibitor inpickling or other metal treating operations with aqueous sulfuric acidsolutions.

The corrosion inhibiting activity of l-ethynylcyclohexanol-l isdemonstrated by the following example. In the example the inhibitorconcentration is expressed as percent by weight of the aqueous sulfuricacid solution in which it is incorporated and the acid concentration ofthe solution is expressed as percent by weight of the solution. Themethod used to determine the corrosion inhibiting properties ofl-ethynylcyclohexanol-l as set forth in the following example employedtest specimens of low carbon 1020 cold-rolled steel. Coupons in. x 1%in. were cut from the steel sheet-stock and pickled in dilute HCl toremove scale and surface film. After pickling they were dipped in sodiumbicarbonate solution, rinsed well in tap water while rubbing with apiece of cotton, rinsed in distilled water and finally dried withacetone. The clean and dry specimens were then weighed to the nearest0.1 mg., all handling being effected with forceps to keep the couponsfree of oil or moisture from the hands. Each inhibitor was weighed andplaced in 100 ml. of the acidic solution. Weighed and identified couponsin duplicate were supported on glass hooks in a 4 oz. glass jar, thesolution being studied added, the jar covered and placed in a constanttemperature oven at 80 C. for 3 hours. At the end of the exposureperiod, the jars were removed from the oven, samples removed, rinsedwith tap water, sodium bicarbonate solution, tap water, distilled waterand finally acetone. The dry coupons were weighed and the percentinhibition calculated by subtracting the loss in weight of the couponfrom the original weight, dividing by the original weight andmultiplying by 100. This is expressed by the following formula:

Percent inhibition The results are expressed as percent inhibition andare the average of the duplicate samples.

Example 2 Using the procedures described above, steel coupons wereimmersed at C. (176 F.) for 3 hours in 4.8 N sulfuric acid containingl-ethynylcyclohexanol-l in concentrations of 0.05% and 0.01% of theacidic solution.

Immersion corrosion rate, percent Inhibitor concentration, percent:

0.01 98 None (control) 10 Immersion Inhibitor Bend Angle Corrosion RatePropargyl alcohol Broke at 80. B0 3-1netl1yl1-butyn-3-ol do 38 It willbe understood that various changes and modifications may be made in theforegoing description without parting from the scope of the invention,as defined in the appended claims and it is intended, therefore, thatall matter contained in the foregoing description shall be interpretedas illustrative only and not as limitative of the invention.

We claim:

1. A method of inhibiting hydrogen-embrittlement of ferrous metals by anaqueous sulfuric acid solution which comprises incorporating in saidsolution an effective inhibiting amount of l-ethynylcyclohexanol-l whilesaid solution is in contact with said metals.

2. A method of inhibiting hydrogen-embrittlement of ferrous metals by anaqueous sulfuric acid solution which comprises incorporating in saidsolution 0.01 to 0.5% by Weight of the solution ofl-ethynylcyclohexanol-l while said solution is in contact with saidmetals.

References Cited UNITED STATES PATENTS 7/1961 Monroe et al 252l46 X12/1963 Stilwell 252-396

1. A METHOD OF INHIBITING HYDROGEN-EMBRITTLEMENT OF FERROUS METALS BY ANAQUEOUS SULFURIC ACID SOLUTION WHICH COMPRISES INCORPORATING IN SAIDSOLUTION AN EFFECTIVE INHIBITING AMOUNT OF 1-ETHYNYLCYCLOHEXANOL-1 WHILESAID SOLUTION IS IN CONTACT WITH SAID METALS.